Dr. Bansal has recently moved to the University of Pennsylvania. Upon completion of several manuscripts which are in preparation, this subpoject will be deleted. We have implemented a three-dimensional 23Na MQ imaging sequence on the 4.7T system. This gradient echo imaging sequence is capable of collecting interleaved SQ and TQ 23Na images with very short echo times (2.5-5 ms). We have used this imaging sequence to study the effect of ischemia in rabbit kidney. Interleaved SQ and TQ filtered 23Na images were collected before and after sacrificing the animal with 32 x 32 x 64 data points over a 50 x 50 x 100 mm3 field of view and 4 ms echo time. The total image data collection time was 4 hours. The SQ image indicates a 4-5 fold greater signal intensity in the medullary region as compared to the cortex. The TQ filtered image of the normal kidney did not show any signal intensity due to the low sensitivity of the technique. However, on death, the renal cortex became clearly visible in the TQ filtered image without any substantial increase in signal intensity in the medullary region. This is mainly because the cortical region of the kidney has a large intracellular space while the medullary region is mainly intraluminal and vascular. These images clearly suggest that increase in MQ filtered signal intensity may be a very good marker of cellular injury. (Service 3) REPORT PERIOD: (09/01/97-08/31/98)